No idea about maths but I guess the universities rep may come more into play. Engineering on the other hand, as long as your university's course is accredited the reputation doesn't matter as much provided you are planing on an engineering career.
Though in general the subjects had (2010/11 tables so a little old)
Electrical and Electronic Engineering - Grad job/Study 74% (55% in grad job only)
Maths - Grad Job/study - 75% (34% in grad job only)